WASHINGTON (CNN) --The FBI found no evidence of any type of terrorism or criminal hacking in its investigation of the August power blackout in the Northeast, but the threat of such action remains a concern, the FBI's top counterterrorism official told a House committee Thursday.

FBI Executive Assistant Director Larry Mefford said the widespread outage represented a "dry run" for what the FBI and other law enforcement agencies could face in the event terrorists were able to exploit vulnerabilities in the power grid.

The FBI established centers in several cities in the states where power was disrupted, not only to help determine whether the blackout stemmed from criminal acts, but also to help coordinate law enforcement efforts if widespread incidents of crime resulted from the electrical disruptions.

Relatively few problems were reported.

The August 14 blackout affected people in eight states and Ontario, Canada.

In morning testimony before the House Energy and Commerce Committee, the chairman of FirstEnergy, the Ohio utility company at the center of the blackout inquiry, insisted it was not solely to blame.

"FirstEnergy believes the outage can only be the result of a combination of events that occurred across the Eastern interconnection," said Peter Burg. "We don't believe that events on any one system could account for the widespread nature of the outage."

FirstEnergy came under scrutiny in the days after the massive power outage when reports showed that three of its transmission lines and one that it co-owns with American Electric Power went down about an hour before the blackout, which affected most of an area containing 50 million customers.

Burg acknowledged that his company's computer system experienced failures.

He did not refer to the chaos and anxiety in FirstEnergy's control room that was depicted in the transcript of a phone conversation released by the House Energy and Commerce Committee Wednesday.

That conversation -- between Jerry Snickey, a FirstEnergy technician and a representative of Midwest Independent Transmission System Operator (MISO), the group that monitors the power grid in the Midwest -- occurred in the hour before the widespread blackout began.

"We have no idea what happened. You guys have anything going on?" Snickey said when questioned about what was happening.

Asked why a transmission line went out, Snickey said, "We have no clue. Our computer is giving us fits too. We don't even know the status of some of the stuff around us."

Burg, asked whether his company had a moral responsibility to alert neighboring utilities about its situation prior to the start of the blackout, said his company didn't think it was in a critical situation at that point.

Later, the panel heard from James Torgerson, president and CEO of Midwest Independent Transmission System Operator. He said FirstEnergy waited about 40 minutes before telling the organization that one of its plants had gone down.

The CEO of an energy firm in neighboring Michigan, Joseph Welch of International Transmission Co., also testified, saying, "The communications mishmash must be unwound."

He had earlier told investigators in a statement that Michigan would have had options that could have forestalled the blackout had it been warned of the problems in Ohio.